On the selection of the state space in nonequilibrium thermodynamics

We address here the question of the choice and interpretation of state variables in the thermodynamical description of systems arbitrarily away from equilibrium. It is presented a discussion of the topic in the framework of informational statistical thermodynamics, an approach based on Gibbs algorithm for nonequilibrium dissipative systems, which provides mechano-statistical foundations to phenomenological theories of irreversible thermodynamics. The theory is applied in the case of a particular system consisting of the mobile carriers in a highly excited photo-injected plasma in semiconductors. The concepts and results thus obtained are tested against experimental data in time-resolved and time-integrated optical laser spectroscopy. It is shown how nonequilibrium thermodynamic variables are evidenced and measured in such experiments. It is also discussed the influence on them of the inclusion of dissipative fluxes among the basic variables.